Several varieties of breakaway couplings are known for the support of light standards, signs, parking meters, and the like. Some of these couplings or connectors are shown in U.S. Pat. Nos. 3,630,474; 3,572,223; 3,349,531 and 3,521,413, the teachings of which are herewith incorporated by reference thereto. Such breakaway connectors or couplings desirably fail readily when the supported structure is subjected to lateral impact such as may be applied by a colliding automobile. However, the coupling must have substantial tensile and compressive strength. Yet such couplings desirably fail under the impact force in such a manner as to substantially reduce accident severity to motorists who are sufficiently unfortunate to be closely involved with the failure of such a coupling. Many breakaway coupling devices employ a shear or sliding mode of crack propagation; i.e., one surface of the ruptured coupling slides over another surface of the coupling during the impact failure process.
It would be desirable if there was available an improved breakaway coupling for support poles, standards and the like.
It would also be desirable if there was available an improved breakaway support assembly of high tensile and compressive strength but which ruptures when rapidly loaded in a direction normal to its direction of maximum strength.
It would also be desirable to have an improved method for the support of standards which provides structures of adequate strength and which fails readily under impact normal to the longitudinal axis of the standard.
It would further be desirable if there were available an improved support assembly employing at least on generally vertically disposed support which, on being impacted by a body such as an automobile, would readily fail from a horizontally directed impact yet have adequate tensile and compressive strength in the vertical direction.
According to the present invention, a combination is provided comprising a generally vertical standard, a base member, a connection member, and means affixed to either the standard or base member for receiving the connection member and thereby releasably coupling the standard to the base member. The coupling means receives the connection member and fractures radially with respect to a generally vertical axis of connection, in response to an impact force being applied to the standard in a generally horizontal direction. The coupling means comprises a coupling body that is generally symmetrically disposed about any plane containing the axis of connection, and has one end thereof having an opening formed therein for receipt of the connection member. A plurality of V-shaped grooves, which define regions of minimum strength, surround the connection member and extend from the connection member receiving end of the body parallel to the axis of connection, and extend at least a distance corresponding to the length of the connection member received by the body, so that upon an impact force in a generally horizontal direction acting upon the standard, the coupling will radially fracture to thereby release the connection member and provide detachment of the standard from the base member. The grooves in the coupling body may extend the entire length of the body, and the body may be formed of aluminum, and either cast or extrude.
Fracture initiating means also may be provided associated with the body member, either in the form of sharpened bottom portions at the end of the coupling body defining the connection member receiving opening, or in the form of slots extending along the length of the grooves from the connection member receiving opening.
A fracture-initiating washer may also be provided in combination with the connection member, standard, and coupling means, the fracture-initiating washer being formed of relatively hard material having one or more teeth formed thereon for cooperation with corresponding slots formed in the coupling means and extending along the length of the grooves therein from the connection member receiving opening thereof. Preferably the fracture-initiating washer is formed of steel, or other material harder than the material forming the coupling means, and the connection member receiving bore extending through the washer is not threaded. Similarly, the top portion of the coupling means extending below the bottom termination of the fracture-initiating slots therein being threaded.
It is the primary object of the present invention to provide an assembly for mounting an upright standard including an inexpensive coupling body that is strong in tension and compression, but will radially fracture easily when the standard is subjected to a horizontal force. This and other objects of the present invention will become apparent from an inspection of the detailed description of the invention, and from the appended claims.